Ruby

• object.c (rb_obj_untrusted): new method Object#untrusted?.
  (rb_obj_untrust): new method Object#untrust.
  (rb_obj_trust): new method Object#trust.
• array.c, debug.c, time.c, include/ruby/ruby.h, re.c, variable.c,
  string.c, io.c, dir.c, vm_method.c, struct.c, class.c, hash.c,
  ruby.c, marshal.c: fixes for Object#untrusted?.
• test/ruby/test_module.rb, test/ruby/test_array.rb,
  test/ruby/test_object.rb, test/ruby/test_string.rb,
  test/ruby/test_marshal.rb, test/ruby/test_hash.rb: added tests for
  Object#untrusted?.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@18568 b2dd03c8-39d4-4d8f-98ff-823fe69b080e